1. Technical Field of the Invention
The present invention relates generally to sheet feeding system suited for sheet feeding in duplicating machines, printing machines etc. and more particularly to a system for automatically sending a sheet of document onto a document frame of an electronic photographic duplicating machine and stopping it in place.
2. Description of the Prior Art
In an electronic photographic duplicating machine, when a sheet feeding system for such as documents is provided above the main unit thereof, a sheet tray and a parting roller used to be normally arranged engageably and disengageably below a first feed roller so that the sheet tray is pressed on by the first feed roller for a sheet to be sent out at a time, while double feeding of sheets is prevented by the parting roller pressed against the first feed roller rotating in the same direction therewith.
In an electronic photographic duplicating machine of such a setup, however, it was often the case that efficient sheet feeding by said function of the parting roller was infeasible as, when the parting roller, for instance, was not functioning well, the sheet tray, once released of the pressure contact with the first feed roller, was pressed again to the first feed roller for feeding of the next sheet, even when the next sheet was already engaged by the first feed roller, this unnecessary step being repeated. Also, there was an inconvenience that when adjacent sheets were partly fed overlappingly (double fed) by the first feeding roller, despite the fact that it did not necessarily result in jamming, the condition could not be distinguished, thus making it difficult to cope readily with possible occurence of jamming.
As the prior art in the technical field of the present invention are known U.S. Pat. No. 3,469,835, U.S. Pat. No. 4,025,187 and U.S. Pat. No. 4,248,528.